The invention relates generally to crushers and, more particularly to a roll crusher having an improved apparatus for adjusting the crushing gap and a method of adjusting the rollers to change the size of the crushed material.
Generally speaking, roll crushers are employed to crush solid material, such as rock or coal. Two roll crushers consist of two parallel rotating crushing rolls, which are spaced apart an amount corresponding to the desired product or particle size of the crushed material. The rolls are driven in opposite directions so that the material to be crushed is drawn into the rolls and discharged from the crusher. The material can be discharged onto a conveyer or other appropriate apparatus for receiving or removing the crushed material. The material also can be conveyed to sizing screens of a particular mesh to separate product of a desired size.
To adjust particle size of the crushed product, the distance between the two rolls, referred to as the crushing gap or nip, is adjusted. To obtain crushed particles of generally smaller size, the gap between the two rolls is reduced in width. To obtain larger crushed particles, the gap is widened. In conventional two roll crushers, one roll is mounted on the crusher frame so as to be moveable toward or away from a stationary roll in a horizontal plane. In general, the movable roll is positioned on a frame and urged toward a fixed roll by springs. Springs are used so that uncrushable material can pass through the crusher by momentarily enlarging the gap between the rolls without damaging the crusher. The spacing between the rolls is varied and maintained by the placement of shims.
The space between the rolls is adjusted not only to change the crushed particle size, but also to retain uniform spacing in the event the rolls wear down. In any event, heretofore the known procedures for adjusting the crushing gap require a shut down of the crusher resulting in downtime, take considerable time and effort, and require the use of rather elaborate springs, shims and hydraulic rams.
It is among the several objects of the present invention to provide a two roll crusher having an improved mechanism for adjusting the crushing gap between the opposed crushing rolls.
Another aspect of the present invention to provide a two roll crusher in which the crushing gap between the opposed crushing rolls can be adjusted by a relatively easy, rapid and safe method.
Another aspect of the present invention to provide a roll crusher in which the principles for adjusting the crushing gap can be imparted to a single roll crusher, if desired.
In accordance with the invention, briefly stated, an improved two roll crusher is provided having a box-like main frame and a housing on the frame with a material inlet and a crushed material discharge outlet. A first motor driven crushing roll is rotatably mounted on the frame within the housing. A second crushing roll is mounted on a roll carriage and also positioned within the housing. The first and second crushing rolls are in an opposed, spaced apart relationship defining a material crushing gap between the first and second rolls. The roll carriage is a generally rectangular frame position atop the main frame. One end of the roll carriage is attached to the main frame near the midpoint of the main frame by pivot. The opposite end of the roll carriage is free. The pivot connecting the crushing roll carriage to the main frame is asymmetrically positioned on the main frame relative to the rotational axes of the crushing rolls. More specifically, the pivot is positioned nearer to the first crushing roll than to the second crushing roll.
An actuator, which in the illustrated embodiment is a worm screw jack, is mounted between the main frame and the free end of the roll carriage. The actuator is used to move the roll carriage about the pivot. Because the pivot is asymmetrically positioned, as the roll carriage is pivoted up, the second crushing roll mounted on the roll carriage moves in an upward arc toward the first crushing roll, thereby decreasing the crushing gap between the first and second crushing rolls. Likewise, a lowering of the roll carriage moves the second crushing roll away from the first crushing roll to widen the crushing gap. The operator can precisely manipulate the actuator to effect known incremental changes in the gap size.
The actuator can be equipped with a servo motor. The servo motor can operate the actuator in response to operator commands or in response to a computer program which, in a closed loop system, appropriately actuates the servo motor in response to the size of crushed material which is sampled along the closed loop, preferably at a sizing screen apparatus. Hence, in the closed loop system, the crushing gap can be adjusted, automatically, in response to crushed material sample size so as to maintain a desired crushed product size.